1. Field of the Disclosure
The present disclosure relates generally to a method for controlling gain in a communication system.
2. Description of the Related Art
In Time Division Synchronous Code Division Multiple Access (TD-SCDMA), a plurality of subscribers execute communication in a single frequency using different time bands, unlike in Code Division Multiple Access (CDMA) or Wideband Code Division Multiple Access (WCDMA), which use multiple transmission/reception frequencies. TD-SCDMA is a Time Division Duplex (TDD) based mobile communication scheme, which transmits or receives a data block based on a time slot (TS). TD-SCDMA uses a mid-amble of a data block as a reference signal, and distinguishes a part of the data block before the reference signal and a part of the data block after the reference signal as Data-1 and Data-2, respectively.
In TD-SCDMA, reception power is different for each data block, and gain may be controlled to adjust a difference in reception powers. For example, a conventional technique, such as Automatic Gain Control (AGC) may be implemented as the gain control method.
A first AGC method executes gain estimation and gain control N times using Data-1, and fixes the last gain. In this method, when data allocation of a TS is executed first, the lowest gain is set as an initial value; otherwise, the last gain of a previous sub-frame is set as an initial value.
A second AGC method calculates an error based on an input power and a target power, and uses an algorithm that changes an AGC loop speed based on the calculated value. Specifically, when a signal is input in a gap section, an error value rapidly increases. The second AGC method increases the speed, based on the increased error value, in order to execute faster AGC. When the error value is adjusted within a predetermined range, the method executes slower AGC. Also, the gain initial value of the AGC is set to a previous convergence value of an error value stored in a memory, by which an AGC stabilization time may be reduced.
The above described first and second AGC methods correspond to AGC operations when a difference in reception powers is high among data blocks, in order to converge a signal on a target level after a predetermined period of time, which indicates that the gain used in a data block and a received signal level may have been different in the part before the reference signal, i.e., Data-1.
However, when a receiver, which is capable of securing high performance at a constant gain for each data block is assumed, the above-described conventional AGC methodologies may not overcome deterioration in performance. Therefore, when the difference in reception powers among blocks is high, there is a desire for a method that enables convergence of signals on a target level in order to overcome performance deterioration.